The present invention relates to a packing plug assembly used in a waterproof connector, especially a packing plug assembly having a structure for preventing insufficient retention of a terminal therein, as well as an electrical connector made employable in an environment exposed to water by using said packing plug assembly.
As the prior art there is known, for example, such a waterproof connector as shown in FIG. 7, in which terminals B and B' inserted in connector housings A and A' are retained by flexible latch arms A and A.sub.1 ', and rubber packing plugs C and C' are fitted in rear portions of the connector housings A and A'; further, the packing plugs are retained by rear holders D and D' and stabilizers B.sub.1 and B.sub.1 ' at the rear ends of the electrical terminals B and B.sub.1 ' are brought into engagement with the packing plugs C and C' to doubly retain the electrical terminals B and B'.
In such structure, however, even when the electrical terminals B and B' are inserted to an incomplete extent, the packing plugs C and C' can be fitted in the connector housings incompletely due to the elasticity of the packing plugs C and C', resulting in that the packing plugs are not retained by the flexible latch arms A.sub.1 and A.sub.1 ' serving as main retainers, not to mention double retention.
In order to overcome the above drawback, the applicant in the present case has proposed a rubber packing plug in a connection (Japanese Laid Open No. 133587/85) in which with respect to a retaining frame comprising a pressing portion and a base portion interconnected through a connecting rod there is integrally formed a rubber plug so as to have an outer peripheral portion larger in diameter than the pressing portion and the base portion while leaving a pressing surface of the pressing portion, and in the pressing portion and the base portion there is formed an electric wire insertion hole for the rubber plug.
In this case, however, there have been the following problems. Since the rubber plug is molded integrally with the retaining frame, the manufacturing cost is apt to become high. Besides, since the connecting rod is not always mounted in parallel with the outer peripheral portion of the rubber plug, elastic deformations of the outer peripheral portion do not become constant and there arises a scatter of sealability.
In order to obtain an electric connector of a high waterseal it is necessary to use a housing of a watertight structure and it is also necessary that the gap between the housing and an electric wire with a terminal inserted and fixed in the housing be of a watertight structure. To this end, usually a packing plug which permits an electric wire to pass therethrough is fitted in a rear opening portion of the housing.
The packing plug is formed of a soft and elastic material, e.g. rubber, to enhance the watertightness. But, because of recovery from the deformation produced when pushing the plug into the rear opening portion of the housing and the resulting return, there easily occur troubles such as incomplete insertion and dislocation of the terminal. According to one method for preventing the occurrence of such troubles, a rear holder serving as means for preventing dislocation of the waterproof plug is provided at a rear end portion of the housing. Even by this method, however, the difficulty of insertion of the waterproof plug is still not improved.